CN106029918A - High-strength steel sheet and method for producing same - Google Patents

High-strength steel sheet and method for producing same Download PDF

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Publication number
CN106029918A
CN106029918A CN201580008832.0A CN201580008832A CN106029918A CN 106029918 A CN106029918 A CN 106029918A CN 201580008832 A CN201580008832 A CN 201580008832A CN 106029918 A CN106029918 A CN 106029918A
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steel plate
steel sheet
temperature
annealing
continuous annealing
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CN106029918B (en
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伏胁祐介
川崎由康
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JFE Engineering Corp
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NKK Corp
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0273—Final recrystallisation annealing
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/26—Methods of annealing
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/008—Ferrous alloys, e.g. steel alloys containing tin
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
    • C25F1/00—Electrolytic cleaning, degreasing, pickling or descaling
    • C25F1/02—Pickling; Descaling
    • C25F1/04—Pickling; Descaling in solution
    • C25F1/06—Iron or steel
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/34—Methods of heating
    • C21D1/42—Induction heating
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
    • C21D8/0447—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the heat treatment
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/25—Process efficiency

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  • Electrochemistry (AREA)
  • Heat Treatment Of Sheet Steel (AREA)
  • Heat Treatment Of Strip Materials And Filament Materials (AREA)

Abstract

Provided is a high-strength steel sheet that has, even when the content of Si or Mn is high, excellent workability, chemical convertibility, and corrosion resistance after electrodeposition coating, and a method for producing said steel sheet. When continuously annealing the steel sheet, the belowmentioned (condition 1)-(condition 3) are employed. (Condition 1) In a heating process during continuous annealing, the steel sheet is heated under conditions in which the temperature increase speed is 7 DEG C/s or more when the internal temperature of an annealing furnace is in a temperature region of between 450 DEG C and A DEG C (A: 500 <= A), inclusive. (Condition 2) The steel sheet maximum attained temperature during continuous annealing is configured to be between 600 DEG C and 750 DEG C, inclusive. (Condition 3) The steel sheet transit time, in which the steel sheet temperature is in a temperature region of between 600 DEG C and 750 DEG C, inclusive, during continuous annealing is configured to be between 30 seconds and 10 minutes, inclusive, and the dew point of the atmosphere to be -10 DEG C or more.

Description

High-strength steel sheet and manufacture method thereof
Technical field
Even if the present invention relates to a kind of chemical conversion treatment also with excellence when the content of Si, Mn is many The high-strength steel sheet of the corrosion resistance after rationality and electrodeposition coating and manufacture method thereof.
Background technology
In recent years, from the viewpoint of the crashworthiness of the fuel consumption efficiency and raising automobile that improve automobile, Realized the thin-walled property of body material by the high intensity of body material, make the lightweight of vehicle body own, And the requirement of high intensity improves.Therefore, high-strength steel sheet application in the car is being promoted.
Generally, automotive sheet carries out application and uses.As the pre-treatment of this application, automobile is used Steel plate is implemented to be referred to as parkerized chemical conversion treatment.The chemical conversion treatment of automotive sheet It is for ensuring that one of important process of corrosion resistance after application.
In order to improve the intensity of steel plate, ductility, steel plate is effectively made to contain Si, Mn.But, When continuous annealing, though Si, Mn will not cause Fe oxidation (by Fe oxide reduce ) N of reproducibility2+H2Also can aoxidize in the case of annealing under gas atmosphere.Because this Si, The oxidation of Mn and be formed selectively the oxide (SiO containing Sn, Mn at surface of steel plate2、MnO Deng.Hereinafter referred to as selective surface's oxide).This selective surface's oxide hinders chemical conversion treatment The reaction of formation of the chemical conversion tunicle in reason, therefore, is formed at surface of steel plate and does not generate chemical conversion The tiny area (hereinafter referred to as uncovered area (ス ケ)) of tunicle, chemical convertibility reduces.
As the prior art of the chemical convertibility improving the steel plate containing Si, Mn, in patent Document 1 discloses use galvanoplastic on steel plate, forms 20～1500mg/m2The side of ferrum coating Method.But, in the method, exist additionally need electroplating device, operation increase and make cost also increase Add such problem.
It addition, in patent documentation 2, improve phosphate treated by regulation Mn/Si ratio, In patent documentation 3, improve phosphate treated by adding Ni.But, this effect depends on The content of Si, Mn in steel plate, needs further to change for the steel plate that the content of Si, Mn is high Kind.
And then, Patent Document 4 discloses following method: dew point during by making annealing for-25～ 0 DEG C, within being 1 μm away from the surface of steel plate degree of depth, form the inside oxygen being made up of the oxide containing Si Changing layer, making the ratio containing Si oxide is shared in surface of steel plate length 10 μm is less than 80%.So And, in the case of the method described in patent documentation 4, premise is that to control the region of dew point be stove Interior entirety, therefore, the controlling difficulty of dew point, it is difficult to stable operation.It addition, at unstable dew When annealing under point control, the distribution of the subscale formed on steel plate confirms Uneven, it is possible on the length direction, width of steel plate, to produce the inequality of chemical convertibility (an overall or part produces uncovered area).And then, even if improve at chemical convertibility In the case of, owing to there is the oxide Han Si, therefore, patent in the underface of chemical conversion treatment tunicle The problem that technology described in document 4 exists the corrosion-resistant after electrodeposition coating.
It addition, recorded following method in patent documentation 5: make steel billet temperature in an oxidizing atmosphere Reach 350～650 DEG C and form oxide-film at surface of steel plate, then, be heated under reducing atmosphere Recrystallization temperature also cools down.But, in the method, by the method that carries out aoxidizing at surface of steel plate The thickness of the oxide film thereon formed there are differences, and aoxidizes the most fully.It addition, In method described in patent documentation 5, oxide film thereon is blocked up sometimes, under reducing atmosphere later Annealing in produce residual or the stripping of oxide-film, surface texture is deteriorated.It addition, at patent documentation 5 Embodiment in, describe the technology carrying out aoxidizing in an atmosphere.Oxidation in an atmosphere exists thicker Ground generates oxide and the problem of reduction after being difficult to or need the reducing gases of high hydrogen concentration The problem of atmosphere.
And then, patent documentation 6 recorded following method: in terms of quality % containing more than 0.1% The cold-rolled steel sheet of Mn of Si and/or more than 1.0%, at steel billet temperature more than 400 DEG C and the oxygen of ferrum Under conditions of under activating QI atmosphere surface of steel plate formed oxide-film, then, under the reducing atmosphere of ferrum on The oxide-film stating surface of steel plate reduces.Specifically, it is following method: steel billet temperature 400 DEG C Above, by the Fe of surface of steel plate under conditions of the straight ignition combustor using air ratio to be 0.93～1.10 After oxidation, at the N of reduction Fe oxide2+H2Steel plate is annealed by gas atmosphere.Thus, press down Make and form, at surface of steel plate, the selective surface's oxide making chemical convertibility deteriorate, at steel plate table Face forms the oxide layer of Fe.The not concrete heating temperature recording straight ignition combustor in patent documentation 6 Degree.But, in patent documentation 6, in the case of containing a large amount of (about more than 0.6%) Si, The amount of oxidation of the Si of oxidation easier than Fe increases, and the oxidation of Fe is suppressed or the oxidation of Fe itself Become very few.Its result, in the technology described in patent documentation 6, the surface Fe after reduction sometimes There is SiO in insufficient or after reduction surface of steel plate that formed of reducing zone2And produce chemical conversion The uncovered area of tunicle.
Prior art literature
Patent documentation
Patent documentation 1: Japanese Unexamined Patent Publication 5-320952 publication
Patent documentation 2: No. 4319559 publications of Japanese Patent No.
Patent documentation 3: No. 2951480 publications of Japanese Patent No.
Patent documentation 4: No. 3840392 publications of Japanese Patent No.
Patent documentation 5: Japanese Laid-Open Patent Publication 55-145122 publication
Patent documentation 6: Japanese Unexamined Patent Publication 2006-45615 publication
Summary of the invention
The present invention makes in view of the foregoing, its object is to, it is provided that though a kind of Si, Also after there is when the content of Mn is many processability of excellence, chemical convertibility, electrodeposition coating The high-strength steel sheet of corrosion resistance and manufacture method thereof.
In above-mentioned patent documentation in described such prior art, only by overall in making annealing furnace Steam partial pressure or oxygen partial pressure rise improve dew point or oxygen concentration, make the inner transition oxygen of steel plate Change.Therefore, as it has been described above, prior art controls at the dew point that stove is overall or deposits in terms of oxidation control In problem, or chemical convertibility produces inequality, or the corrosion resistance after electrodeposition coating is bad Change.
Therefore, the present inventor etc. solve problem to the new method by being provided without in conventional idea Method is studied.It is found that by being likely to become the corrosion resistance after electrodeposition coating The tissue on steel plate top layer of starting point of deterioration, structure carry out the control of higher degree, can improve high strength steel Corrosion resistance after the chemical convertibility of plate and electrodeposition coating.Specifically, steel plate is being entered Following (condition 1)～(condition 3) is used during row continuous annealing.
(condition 1), in the heating process of continuous annealing, is 450 DEG C～A DEG C at annealing in-furnace temperature In the temperature province of (A:500≤A), to steel plate under conditions of programming rate is 7 DEG C/more than s Heat.
Steel plate maximum temperature reached, in continuous annealing, is set to 600 DEG C～750 DEG C by (condition 2).
(condition 3) in continuous annealing, by the temperature province that steel billet temperature is 600 DEG C～750 DEG C Steel plate was set to 30 seconds～10 minutes by the time, and the dew point of atmosphere is set to more than-10 DEG C.
By carrying out such process, it is possible to selective surface's diffusion of suppression Si, Mn etc., oxidation (hereinafter referred to as surface segregation).Its result, available chemical convertibility, processability and electricity sink The high-strength steel sheet of the excellent corrosion resistance after long-pending application.
The tissue on steel plate top layer of high-strength steel sheet, the structure that are obtained by above method have following Feature 1,2.
(feature 1) has each list in the region within surface of steel plate 100 μm of high-strength steel sheet Face adds up to 0.010～0.050g/m2Selected from Fe, Si, Mn, Al, P, B, Nb, Ti, Cr, The oxide of at least one in Mo, Cu, Ni, Sn, Sb, Ta, W and V.
(feature 2) in the region within surface of steel plate 10 μm within steel plate crystal boundary 1 μm Crystal grain in there is the oxide containing crystallinity Mn system oxide.
By becoming the steel plate top layer having the feature that, that can suppress after electrodeposition coating is corrosion-resistant The deterioration of property, excellent in chemical convertibility.
The present invention is based on above-mentioned opinion, and feature is as follows.
(1) manufacture method of a kind of high-strength steel sheet, it is characterised in that containing in terms of quality % C:0.03～0.35%, Si:0.01～0.50%, Mn:3.6～8.0%, Al:0.01～1.0%, The steel that below P:0.10%, below S:0.010% and surplus are made up of Fe and inevitable impurity When plate carries out continuous annealing, in the heating process of described continuous annealing, at annealing in-furnace temperature it is In the temperature province of 450 DEG C～A DEG C (A:500≤A), at the bar that programming rate is 7 DEG C/more than s Under part, described steel plate is heated, in described continuous annealing, steel plate maximum temperature reached is set to 600 DEG C～750 DEG C, in described continuous annealing, be 600 DEG C～the humidity province of 750 DEG C by steel billet temperature The steel plate in territory was set to 30 seconds～10 minutes by the time, and the dew point of atmosphere is set to more than-10 DEG C.
(2) according to the manufacture method of the high-strength steel sheet described in (1), it is characterised in that described steel Plate, is grouped into as one-tenth, in terms of quality % possibly together with selected from B:0.001～0.005%, Nb:0.005～ 0.05%, Ti:0.005～0.05%, Cr:0.001～1.0%, Mo:0.05～1.0%, Cu: 0.05～1.0%, Ni:0.05～1.0%, Sn:0.001～0.20%, Sb:0.001～0.20%, In Ta:0.001～0.10%, W:0.001～0.10% and V:0.001～0.10% more than a kind Element.
Manufacture method according to the high-strength steel sheet described in (1) or (2), it is characterised in that After carrying out described continuous annealing, in containing sulfur aqueous acid, carry out cathodic pickling.
(4) a kind of high-strength steel sheet, it is characterised in that there is the one-tenth packet described in (1) or (2) Become, have in the region within surface of steel plate 100 μm each one side add up to 0.010～ 0.050g/m2Selected from Fe, Si, Mn, Al, P, B, Nb, Ti, Cr, Mo, Cu, Ni, Oxide more than at least one in Sn, Sb, Ta, W and V, further away from surface of steel plate In the crystal grain within steel plate crystal boundary 1 μm in region within 10 μm, there is the oxidation containing Mn Thing.
According to the present invention, though available also there is excellence when the content of Si, Mn is many processability, The high-strength steel sheet of the corrosion resistance after chemical convertibility and electrodeposition coating.
It addition, according to the present invention, it is also possible to obtain excellent appearance and have excellence processability, The high-strength steel sheet of the corrosion resistance after chemical convertibility and electrodeposition coating.
Should illustrate, excellent in chemical convertibility refers to have not covering after not having chemical conversion treatment Cover region territory, uneven outward appearance.Become outside excellence by suppression uncovered area, uneven generation See.
Detailed description of the invention
Hereinafter, embodiments of the present invention are illustrated.Should illustrate, the present invention is not limited to Following embodiment.
Below the manufacture method of the high-strength steel sheet of the present invention uses when steel plate carries out continuous annealing (condition 1)～(condition 3).
(condition 1), in the heating process of continuous annealing, is 450 DEG C～A DEG C at annealing in-furnace temperature In the temperature province of (500≤A), under conditions of programming rate is 7 DEG C/more than s, steel plate is carried out Heating.
Steel plate maximum temperature reached, in continuous annealing, is set to 600 DEG C～750 DEG C by (condition 2).
(condition 3) in continuous annealing, by the temperature province that steel billet temperature is 600 DEG C～750 DEG C Steel plate was set to 30 seconds～10 minutes by the time, and the dew point of atmosphere is set to more than-10 DEG C.
First, the manufacture method of the steel plate of the object as continuous annealing is illustrated.The system of steel plate The method of making is not particularly limited.Such as can use the method that steel hot rolling is manufactured hot rolled plate；By steel After hot rolling, carry out method that is cold rolling and that manufacture cold-reduced sheet；After steel hot rolling, carry out pickling, cold rolling and Manufacture the method etc. of cold-reduced sheet.Can be used as to move back continuously by the hot rolled plate as above obtained, cold-reduced sheet The object of fire.
Should illustrate, the condition of hot rolling when manufacturing above-mentioned steel plate, the condition of pickling are not particularly limited, As long as suitably setting.It addition, for cold rolling, preferably carry out with the reduction ratio of 40%～80%. When reduction ratio is less than 40%, recrystallization temperature generation low temperature, therefore, mechanical property easily deteriorates. On the other hand, when reduction ratio is more than 80%, owing to for high-strength steel sheet, therefore, not only rolling cost Rise, and surface segregation when annealing increases, sometimes chemical convertibility deterioration.
Then, illustrate by the operation of steel plate continuous annealing.Continuous annealing can use general company Continuous annealing device is carried out.The annealing furnace that general continuous annealing apparatus is had has heating at leading portion Carry, at back segment, there is soaking zone.Generally, in the heating tape of leading portion, steel plate is heated to set point of temperature, In the soaking zone of back segment in set point of temperature, under conditions of the stipulated time, keep steel plate.
It is a feature of the present invention that and use above-mentioned (condition 1)～(condition 3) when continuous annealing.
As described in above-mentioned (condition 1), with in the heating process of continuous annealing, in annealing furnace Temperature is in the temperature province of 450 DEG C～A DEG C (A:500≤A), and programming rate is 7 DEG C/more than s Mode be controlled and heat.By this heating, it can be made to pass through as soon as possible will not inside steel plate There is the oxidation (hereinafter referred to as internal oxidation) of easily oxidizable element (Si, Mn etc.) but can occur The temperature province of 450 DEG C of surface segregation～A DEG C (A:500≤A), it is possible to suppression surface segregation. That is, the uncovered area after chemical conversion treatment, unequal can be suppressed.
The effect that chemical convertibility as above improves owns (condition 1)～(bar by carrying out Part 3) and produce.It is especially considering that (condition 1), (condition 3) are the most important.As it has been described above, (condition 1) is utilized to suppress the generation of surface segregation thing as far as possible.And then, utilize (condition 3) to pass through Inside the steel plate within surface of steel plate 10 μm, there is subscale in right amount, can suppress to make annealing After chemical convertibility deterioration steel in Si, Mn etc. at the surface segregation of surface of steel plate.Thus, Can obtain not having uncovered area, uneven excellent chemical convertibility and higher electro-deposition to be coated with Corrosion resistance after dress.
In the present invention, for using (condition 1)～the reason of (condition 3), enter in detail below Row explanation.
As described in above-mentioned (condition 1), in the heating process of annealing, at annealing in-furnace temperature it is In the temperature province of 450 DEG C～A DEG C (wherein, A is the arbitrary value selected from 500≤A), Will heat up speed and be set to 7 DEG C/more than s.This heating is generally carried out in heating tape.Should illustrate, should The temperature of temperature province refers to carry out the temperature (steel billet temperature) of the steel plate annealed.If steel billet temperature The roller position using each passage in annealing furnace thermometer is set and carry out thermometric and the value that obtains i.e. Can.It addition, as thermometer, multipath reflection thermometer and radiation thermometer etc., thermometer can be illustrated Mode be not particularly limited.
The temperature province controlling programming rate is set to the reason of more than 450 DEG C as follows.Less than 450 DEG C Temperature province in, uncovered area, uneven generation, the deterioration etc. of corrosion resistance will not be caused to become The surface segregation of degree, internal oxidation for problem.Therefore, the temperature province controlling programming rate sets For presenting more than temperature province that is 450 DEG C of the effect of the present invention.
It addition, the temperature province controlling programming rate is set to less than A DEG C, (A is for from 500≤A The arbitrary value selected) reason as follows.First, the upper limit of the temperature province controlling programming rate is low In 500 DEG C time, will heat up the time that speed controlling is 7 DEG C/more than s short, it is impossible to obtain this fully Bright effect.Therefore, A is set to more than 500 DEG C.It addition, control the temperature province of programming rate When the upper limit is more than 600 DEG C, no problem to the effect of the present invention.But, when the upper limit is more than 600 DEG C, From the viewpoint of the cost that equipment spends in annealing furnace increases (setting up of sensing heater), become It is unfavorable to obtain.It is therefore preferable that less than 600 DEG C.
By as follows for reason that the programming rate in said temperature region is set to 7 DEG C/more than s.Start to confirm To surface segregation inhibition be 7 DEG C/more than s of programming rate.The upper limit of programming rate does not has spy Do not limit, but when 500 DEG C/more than s, effect is saturated, become unfavorable becoming present aspect.Therefore, Programming rate preferably 500 DEG C/below s.Should illustrate, such as can by steel billet temperature be 450 DEG C～ In the annealing furnace of A DEG C, configuration senses heater and makes programming rate is 7 DEG C/more than s.
As described in above-mentioned (condition 2), in annealing, steel plate maximum temperature reached is set to 600 DEG C～ 750℃.Above-mentioned steel plate maximum temperature reached except A DEG C of situation identical with steel plate maximum temperature reached with Outward, be above-mentioned from heating process add the further heating of maximum temperature reached A DEG C hankered make and on The temperature risen.Here, steel plate maximum temperature reached refers to utilizing the mensuration side with above-mentioned steel billet temperature When the method that method is identical measures, annealing reaches the highest value.
By as follows for reason that the steel plate maximum temperature reached in annealing furnace is set to 600 DEG C～750 DEG C.Steel plate When maximum temperature reached is less than 600 DEG C, it is impossible to obtain good material.Therefore, in the present invention, Above-mentioned steel plate maximum temperature reached is set to more than 600 DEG C.On the other hand, steel plate maximum temperature reached During more than 750 DEG C, surface segregation becomes notable, starts to confirm the deterioration etc. of chemical convertibility. And then, from the viewpoint of material, when steel plate maximum temperature reached is more than 750 DEG C, intensity and extension The effect of the balance of property is saturated.Thus, steel plate maximum temperature reached is set to 600 DEG C～750 DEG C.
As described in above-mentioned (condition 3), it is 600 DEG C～the temperature of 750 DEG C by steel billet temperature in annealing The steel plate in region was set to 30 seconds～10 minutes by the time, and the dew point of atmosphere is set to more than-10 DEG C.
If above-mentioned steel plate less than 30 seconds, then cannot obtain target materials (TS, El) by the time. On the other hand, if above-mentioned steel plate by the time more than 10 minutes, then the effect of the balance of intensity and ductility The most saturated.
The dew point of the atmosphere of the temperature province that steel billet temperature is 600 DEG C～750 DEG C is set to by annealing- When more than 10 DEG C, make by H because of the rising of dew point2O decomposes the O produced2Gesture rises, and can promote Internal oxidation.In the temperature province less than-10 DEG C, the formation amount of internal oxidation is few.It addition, it is right The upper limit in dew point is not particularly limited.But, when dew point is more than 90 DEG C, the oxidation quantitative change of Fe is many, It is likely to occur annealing furnace wall, the deterioration of roller.Therefore, dew point preferably less than 90 DEG C.
It addition, the dew point of other temperature province is not particularly limited, as long as being such as-10～-40 DEG C Scope.
In annealing, use above-mentioned (condition 1)～(condition 3) for obtaining the chemistry with excellence The high-strength steel sheet of the corrosion resistance after conversion processing and electrodeposition coating is important.Above-mentioned necessity The condition in annealing beyond condition is as follows.
In the present invention, the soaking temperature in soaking zone, the condition of soaking time are not particularly limited, As long as suitably setting.
In above-mentioned continuous annealing, as long as in the scope of the effect not damaging the present invention, then the gas of atmosphere Body is not particularly limited.Generally, the gas of atmosphere is by hydrogen, nitrogen and inevitable foreign gas Constitute.As long as it addition, in the scope of the effect not damaging the present invention, then can also contain beyond them Gas (H2O、CO2, CO etc.).
In the present invention, it is preferred to make the density of hydrogen of the atmosphere in continuous annealing be 1vol%～ 50vol%.When density of hydrogen is less than 1vol%, sometimes can not get the activation effect brought by reduction, change Learn conversion processing deterioration.The upper limit does not has special provision, but during more than 50vol%, in order to improve hydrogen Gas concentration and make manufacturing cost increase, and saturated by adjusting effect produced by density of hydrogen.Therefore, Preferred 1vol%～50vol% of density of hydrogen.And then, preferably 5vol%～30vol%.
In the manufacture method of the present invention, after continuous annealing, it is possible to implement following process.
By high-strength steel sheet after the temperature province cooling of 600 DEG C～750 DEG C, can carry out as required Quenching, tempering.Quenching, the condition of tempering are not particularly limited.Tempering is preferably at 150～400 DEG C At a temperature of carry out.During this is because be less than 150 DEG C, there is the trend of the deterioration in elongation of steel plate, super When crossing 400 DEG C, there is the trend that the hardness of steel plate reduces.
It addition, in the present invention, even if not implementing cathodic pickling to also ensure that good chemical conversion treatment Rationality.But, the surface segregation thing of trace in order to be inevitably generated when annealing remove and Guarantee better chemical convertibility, preferably to the high-strength steel sheet after continuous annealing containing sulfur Aqueous acid carries out cathodic pickling.
The pickle used in cathodic pickling is not particularly limited.But, nitric acid, Fluohydric acid. are to equipment Corrosivity strong, operationally it is noted that therefore the most preferred.It addition, hydrochloric acid likely produces from negative electrode Raw chlorine, thus the most preferred.Therefore, if considering corrosivity, environment, then sulphuric acid is preferably used.Sulphuric acid Concentration preferably 5 mass %～20 mass %.When sulfuric acid concentration is less than 5 mass %, electrical conductivity step-down, Therefore, bath voltage when being sometimes electrolysed rises, and power supply load becomes big.On the other hand, sulfuric acid concentration surpasses When crossing 20 mass %, the loss caused by drag-out (drugout) become big, become becoming present aspect For problem.
The condition of cathodic pickling is not particularly limited.In order to inevitably send out formed after annealing The oxide of Si, Mn of having given birth to surface segregation removes effectively, it is preferred to use electric current density is 1A/dm2 Above alternation electrolysis.The reason using alternation electrolysis is as follows.In the state that steel plate is maintained at negative electrode Time lower, pickling effect will be little.It addition, the Fe of dissolution when being electrolysed when steel plate being maintained at anode Being accumulated in pickle, the Fe concentration in pickle increases, when Fe is attached on surface of steel plate, and meeting Produce problems such as being dried dirt.
The temperature of electrolyte preferably 40 DEG C～70 DEG C.The heating produced by continuous electrolysis can make bath temperature Rise, therefore, be sometimes difficult to be maintained at a below temperature 40 DEG C.It addition, from the lining of electrolysis bath From the viewpoint of durability, preferable temperature is not more than 70 DEG C.During it addition, be less than 40 DEG C, pickling effect Diminish, it is therefore preferable that more than 40 DEG C.
As it has been described above, the continuous annealing condition that the present invention is steel plate has the manufacture method of feature.To work Steel plate for the object of this continuous annealing illustrates." % " in the explanation that following one-tenth is grouped into Refer to " quality % ".
C:0.03～0.35%
C improves processability by forming martensite etc. in structure of steel.Accordingly, it would be desirable to make containing of C Amount is more than 0.03%.On the other hand, when the content of C is more than 0.35%, intensity excessively rises, and stretches Long rate reduces, and as result, processability deteriorates.Therefore, C amount is set to 0.03%～0.35%.
Si:0.01～0.50%
Si is to obtain the effective element of good material for strengthening steel.But, Si is easily oxidizable Element, therefore, unfavorable in terms of chemical convertibility.Considering from this viewpoint, Si is should be as far as possible Avoid the element added.It addition, inevitably contain the Si of about 0.01% in steel, in order to make The content of Si is reduced to cause cost increase below it.As it has been described above, the content of Si with 0.01% is Lower limit.On the other hand, when the content of Si is more than 0.50%, the strengthening ability of steel, percentage elongation improve effect The most saturated.It addition, the chemical convertibility deterioration of high-strength steel sheet.Therefore, Si amount be set to 0.01%～ 0.50%.Even if one of inventive feature is also to improve chemical conversion treatment when the content of Si is many This point of property.
Mn:3.6～8.0%
Mn is the effective element of the high intensityization for steel.In order to ensure mechanical property, intensity, need The content of Mn to be made is more than 3.6%.On the other hand, when the content of Mn is more than 8.0%, it is difficult to Guarantee chemical convertibility, it is difficult to guarantee the balance of intensity and ductility.And then, becoming present aspect Become unfavorable.Therefore, Mn amount is set to 3.6%～8.0%.
Al:0.01～1.0%
Al adds for the purpose by deoxidation of molten steel.When the content of Al is less than 0.01%, it is impossible to realize This purpose.The effect of the deoxidation of molten steel is more than 0.01% to obtain by making the content of Al.The opposing party Face, when the content of Al is more than 1.0%, cost increase.And then, when the content of Al is more than 1.0%, The surface segregation of Al becomes many, it is difficult to improve chemical convertibility.Therefore, Al amount be set to 0.01%～ 1.0%.
Below P:0.10%
P is one of element of inevitably containing, it is also possible to do not contain.In order to the content making P is low In 0.005%, it is possible to cost increases, therefore, the content of P preferably more than 0.005%.The opposing party Face, when the content of P is more than 0.10%, weldability deteriorates.And then, when the content of P is more than 0.10%, The deterioration of chemical convertibility becomes violent, is also difficult to even from the present invention improve chemical conversion treatment Rationality.Therefore, P amount is set to less than 0.10%, as lower limit, and preferably 0.005%.
Below S:0.010%
S is one of element of inevitably containing, it is also possible to do not contain S.The lower limit of the content of S does not has There is regulation.When the content of S becomes a large amount of, weldability and corrosion resistance deterioration.Therefore, the content of S It is set to less than 0.010%.
It addition, the surface quality of high-strength steel sheet in order to realize being manufactured by the manufacture method of the present invention, The improvement of the balance of intensity and ductility, implements the steel plate of continuous annealing and can contain as required and be selected from B:0.001～0.005%, Nb:0.005～0.05%, Ti:0.005～0.05%, Cr:0.001～ 1.0%, Mo:0.05～1.0%, Cu:0.05～1.0%, Ni:0.05～1.0%, Sn:0.001～ 0.20%, Sb:0.001～0.20%, Ta:0.001～0.10%, W:0.001～0.10%, V: The element of more than a kind in 0.001～0.10%.Restriction reason containing proper content during these elements By as follows.
B:0.001～0.005%
When the content of B is less than 0.001%, it is difficult to obtain the facilitation effect that quenches.On the other hand, the containing of B When amount is more than 0.005%, chemical convertibility deterioration sometimes.Therefore, when containing B, B measures It is preferably set to 0.001%～0.005%.But, it is judged as without containing in terms of mechanical property improvement During B, steel plate is without containing B.It is also same for containing the arbitrary element for other as required.
Nb:0.005～0.05%
When the content of Nb is less than 0.005%, it is difficult to the effect of adjusted intensity.On the other hand, Nb Content more than 0.05% time, cause cost increase.Therefore, when containing Nb, Nb amount is set to 0.005%～0.05%.
Ti:0.005～0.05%
When the content of Ti is less than 0.005%, it is difficult to the effect of adjusted intensity.On the other hand, Ti Content more than 0.05% time, occasionally result in the deterioration of chemical convertibility.Therefore, containing Ti Time, Ti amount is preferably set to 0.005%～0.05%.
Cr:0.001～1.0%
When the content of Cr is less than 0.001%, it is difficult to obtain quenching degree effect.On the other hand, the containing of Cr When amount is more than 1.0%, there is surface segregation in Cr, therefore, weldability deteriorates.Therefore, containing Cr Time, Cr amount is preferably set to 0.001%～1.0%.
Mo:0.05～1.0%
When the content of Mo is less than 0.05%, it is difficult to the effect of adjusted intensity.On the other hand, Mo Content more than 1.0% time, cause cost increase.Therefore, when containing Mo, Mo amount preferably sets It is 0.05%～1.0%.
Cu:0.05～1.0%
When the content of Cu is less than 0.05%, it is difficult to obtain remaining γ phase and form facilitation effect.On the other hand, When the content of Cu is more than 1.0%, cause cost increase.Therefore, when containing Cu, Cu amount is preferably It is set to 0.05%～1.0%.
Ni:0.05～1.0%
When the content of Ni is less than 0.05%, it is difficult to obtain remaining γ phase and form facilitation effect.On the other hand, When the content of Ni is more than 1.0%, cause cost increase.Therefore, when containing Ni, Ni amount preferably sets It is 0.05%～1.0%.
Sn:0.001～0.20%, Sb:0.001～0.20%
From suppression the nitridation of surface of steel plate, oxidation or produce because of oxidation micro-away from surface of steel plate tens From the viewpoint of the decarburization in rice region, Sn, Sb can be contained.By suppression nitridation, oxidation, can prevent Only the growing amount at surface of steel plate martensite reduces, the fatigue properties of the high-strength steel sheet obtained, surface Quality improving.From the viewpoint of above, when containing Sn and/or Sb, the most all it is set to 0.001% Above content.During it addition, arbitrary content is more than 0.20%, cause the deterioration of toughness, therefore, it Content be preferably set to less than 0.20%.
Ta:0.001～0.10%
Ta by with C, N formed carbide, carbonitride and contribute to high intensity, additionally aid High yield ratio (high YR) is changed.And then, Ta has the effect that hot rolled plate is organized miniaturization, utilizes This effect, cold rolling, annealing after ferrite particle diameter be micronized.And, along with the increasing of grain boundary area Big C segregation in crystal boundary increases, available height sintering hardening capacity (BH amount).From such Viewpoint considers, can be containing the Ta of more than 0.001%.On the other hand, the content of Ta is more than 0.10% Time, not only resulting in cost of material increases, and likely hinders the geneva in the cooling procedure after annealing The formation of body.And then, the deformation drag when TaC separated out in hot rolled plate improves cold rolling, the most surely Fixed actual production becomes difficulty.Therefore, when containing Ta, its content be preferably set to 0.10% with Under.
W:0.001～0.10%, V:0.001～0.10%
W and V, for having formation carbonitride, utilizes and separates out effect by the unit of the effect of steel high intensity Element, can be added as needed on.Such act on interpolation W and/or V time, all contain 0.001% with Upper just confirm.On the other hand, when the content of these elements is more than 0.10%, the excessive high intensity of steel plate Change, sometimes ductility deterioration.As it has been described above, when containing W and/or V, preferred content is 0.001%～0.10%.
Surplus other than the above is Fe and inevitable impurity.Even if the element containing above-mentioned record with Outer element, does not results in any harmful effect to the present invention yet, and its upper limit is set to 0.10%.
Be there is the condition of the continuous annealing becoming the steel plate being grouped into as above by adjustment, available The high-strength steel sheet of the excellent corrosion resistance after processability, chemical convertibility and electrodeposition coating. Hereinafter, this high-strength steel sheet is illustrated.
For containing Si and the high-strength steel sheet of substantial amounts of Mn, resistance in order to meet after electrodeposition coating Corrosivity, needs more highly to control to be likely to become the steel plate top layer of the starting point of the crackle etc. of corrosion Tissue, structure.Therefore, in the present invention, first of all for guaranteeing chemical convertibility, continuously Annealing controls dew point, improves oxygen gesture.By improve oxygen gesture, as easily oxidizable element Si, Mn etc. will occur internal oxidation before carrying out chemical conversion treatment in advance, Si in surface of steel plate, The activity of Mn reduces.And, the external oxidation of these elements is inhibited, result chemical conversion treatment Corrosion resistance after rationality and electrodeposition coating is improved.Specifically, by the manufacture of the present invention The tissue on steel plate top layer of the hardness of steel steel plate of method manufacture, structure have following feature.
(feature 1) has each list in the region within surface of steel plate 100 μm of high-strength steel sheet Face adds up to 0.010～0.050g/m2Selected from Fe, Si, Mn, Al, P, B, Nb, Ti, Cr, Oxide more than at least one in Mo, Cu, Ni, Sn, Sb, Ta, W and V.
(feature 2) in the region within surface of steel plate 10 μm within steel plate crystal boundary 1 μm Crystal grain in there is the oxide containing Mn.
As described in above-mentioned (feature 1), exist every in the region within surface of steel plate 100 μm Individual one side adds up to 0.010g/m2Above selected from Fe, Si, Mn, Al, P and B, Nb, Ti, Oxide more than at least one in Cr, Mo, Cu, Ni, Sn, Sb, Ta, W and V. Thus, the corrosion resistance after chemical convertibility and electrodeposition coating is improved.The formation amount of oxide More than 0.050g/m2Time, it is possible to become the starting point of the crackle of corrosion.Even if it addition, for exceeding 0.050g/m2Formation amount, it is saturated that chemical convertibility improves effect, it is therefore not necessary to by formation amount It is set to more than 0.050g/m2Amount.
As described in above-mentioned (feature 2), in the region within surface of steel plate 10 μm away from In crystal grain within steel plate crystal boundary 1 μm, there is the oxide containing Mn.Subscale exists only in Crystal boundary and time in being not present in crystal grain, the grain boundary decision of easily oxidizable element in steel can be suppressed, but have Shi Wufa is adequately suppressed crystal grain internal diffusion.Therefore, in the present invention, as it has been described above, by with Annealing in-furnace temperature is in the temperature province of 450 DEG C～A DEG C (A:500≤A≤600), and heat up speed Degree is that the mode of 7 DEG C/more than s is controlled, not only in crystal boundary generation internal oxidation, and at crystal grain The most also there is internal oxidation.Specifically, in the region within surface of steel plate 10 μm, away from Crystallinity Si, Mn system oxide is there is in matrix grain within crystal boundary 1 μm.Due at above-mentioned grain Inside there is oxide, the amount of solid solution Si, Mn in the crystal grain near oxide reduces.Its result, Can suppress because of the segregation on surface caused by the crystal grain internal diffusion of Si, Mn.
It addition, the structure of the surface of steel plate of the high-strength steel sheet obtained by the manufacture method of the present invention is such as Upper described, but such as away from surface of steel plate more than in the region of 100 μm, even if above-mentioned oxide growth The most no problem.It addition, away from surface of steel plate more than in the region of 10 μm, away from crystal boundary 1 μm with On crystal grain in there is crystallinity Si, Mn system oxide the most no problem.
The high-strength steel sheet of the present invention can be above-mentioned high-strength steel sheet to be implemented chemical conversion treatment form Steel plate.The kind of chemical conversion treatment solution is not particularly limited, it is possible to use chromate treating solution, The general treatment fluids such as non-chromate treatment fluid.It addition, the most do not limit for chemical conversion processing method Fixed, the various methods such as dipping (dip) process, spraying treatment, electrolysis process can be applied.
The high-strength steel sheet of the present invention can be to implement above-mentioned chemical conversion treatment by electrodeposition coating The steel plate of film is formed on the chemical conversion tunicle of the steel plate of reason.The condition of electrodeposition coating does not has It is particularly limited to, as long as suitably setting.
Embodiment
Hereinafter, based on embodiment, the present invention is specifically illustrated.
Steel as shown in Table 1 is formed the hot rolled steel plate constituted and carries out pickling, after removing casting skin oxide skin, Carry out cold rolling, obtain the cold-rolled steel sheet of thickness 1.0mm.Should illustrate, a part not implemented cold rolling, Directly use the hot rolled steel plate (thickness 2.0mm) after removing casting skin oxide skin.
Then, cold-rolled steel sheet obtained above and hot rolled steel plate are loaded continuous annealing apparatus.In annealing In equipment, as table 2-1 and table 2-2 (is incorporated as table 2, by table 3-1 and table 3 by table 2,3 -2-in-1 and as table 3) shown in, to the steel billet temperature in annealing furnace be 450 DEG C～A DEG C of (A:500 ≤ A≤600) temperature province in programming rate, 600 DEG C～750 DEG C temperature province in dew point It is controlled by time, steel plate maximum temperature reached with steel plate and carries out logical plate, annealing.It addition, The dew point controlled in the annealing furnace beyond the region of above-mentioned dew point is set to-35 DEG C.Dew point is by absorbing The moisture removed in atmosphere controls.It addition, in the present embodiment, the gas componant of atmosphere by nitrogen, Hydrogen and inevitable foreign gas are constituted.Density of hydrogen in atmosphere is set to 10vol%.
After carrying out continuous annealing, after shrend, carry out the tempering of 300 DEG C × 140s.Except No.32～35 In addition, using the high-strength steel sheet that obtained by this tempering as material to be tested.For No.32～35, After above-mentioned tempering, next 40 DEG C, in the aqueous sulfuric acid of 5%, at the electric current shown in table 2 Carry out cathodic pickling under density conditions, obtain material to be tested.In cathodic pickling, material to be tested is pressed Order according to anode, negative electrode carries out the alternation electrolysis of each 3 seconds.
To by operating material to be tested mensuration TS, the El obtained above.It addition, to chemical conversion treatment Corrosion resistance, processability after property and electrodeposition coating are investigated.It addition, to away from surface of steel plate The amount (internal oxidation amount) of the oxide that the region of 100 μm exists is measured.Show the result in table 2、3.It addition, assay method described below and evaluation criterion.
＜ hot strength (TS), percentage elongation (El) ＞
According to the Tensile Testing Method of Metallic Materials according to JIS Z 2241 to hot strength (TS), stretch Long rate (El) is measured.Measurement result is for the evaluation of processability described later.
＜ chemical convertibility ＞
The evaluation methodology of chemical convertibility is as follows.Chemical conversion treatment solution uses Japan The chemical conversion treatment solution (Palbond L3080 (registered trade mark)) of Parkerizing company, Following method is utilized to implement chemical conversion treatment.
By the material to be tested degreaser Fine Cleaner (registrar of Parkerizing company of Japan Mark) carry out defat after, wash, then, with Japan Parkerizing company surface adjust The surface that whole liquid Prepalene Z (registered trade mark) is carried out 30 seconds adjusts.After surface adjusts, Dipping is after 120 seconds in the chemical conversion treatment solution (Palbond L3080) of 43 DEG C, carries out washing, heat Air-dry dry.
By the material to be tested after chemical conversion treatment with scanning electron microscope (SEM) in multiplying power 500 5 visuals field are observed randomly under conditions of Bei.By image procossing to chemical conversion treatment tunicle not Overlay area area occupation ratio is measured, and carries out following evaluation by uncovered area area occupation ratio.“○” For qualified level.
Less than zero: 10%
×: more than 10%
Corrosion resistance ＞ after ＜ electrodeposition coating
Cut out from the chemical conversion treatment steel plate obtained by above-mentioned method size 70mm × The test film of 150mm, with the PN-150G (registered trade mark) of Nippon Paint Co., Ltd. carry out sun from Sub-electrodeposition coating (sintering condition: 170 DEG C × 20 minutes, thickness 25 μm).Then, by end It is not evaluated the face Al rubber belt sealing of side, marks ten strokes arriving surface of steel plate with cutter Lattice (intersecting angle 60 °), as test specimen.
Then, after test specimen is impregnated 240 hours in 5%NaCl aqueous solution (55 DEG C), take Go out, washing, after drying, ten stroke lattice parts are carried out adhesive tape stripping, measure and peel off width.To this Measurement result is evaluated according to following evaluation criterion."○" is qualified level.
Zero: it is unilateral less than 2.5mm for peeling off width
×: it is unilateral for more than 2.5mm for peeling off width
＜ processability ＞
For processability, from material to be tested, edge is that JIS5 is taked in 90 ° of directions relative to rolling direction Number tension test sheet, enters with the condition of crosshead speed 10mm/min according to the regulation of JIS Z 2241 Row tension test, measures hot strength TS (MPa) and percentage elongation El (%), by TS × El >= The situation of 24000 is set to well, be set to bad by the situation of TS × El ＜ 24000.
Internal oxidation amount ＞ in ＜ region within the μm of steel plate top layer 100
Internal oxidation amount is measured by " pulse stove melts-infrared absorption ".But, need Oxygen amount contained in material to be deducted (that is, implementing the steel plate before annealing).In the present invention, to from Oxygen in the steel of the position that more than 100 μm are ground on the two sides of the high-strength steel sheet after continuous annealing respectively Concentration is measured, using this measured value as oxygen amount OH contained in material.It addition, to moving back continuously In the steel that the thickness of slab direction on the high-strength steel sheet surface after fire is overall, oxygen concentration is measured, by this mensuration Value is as oxygen amount OI after internal oxidation.After using the internal oxidation of the high-strength steel sheet as above obtained Oxygen amount OH contained in oxygen amount OI and material, calculates the difference (=OI-OH) of OI Yu OH, And then, it is scaled every one side unit are (i.e. 1m2) the value (g/m of amount2), as internal oxygen Change amount.
Evaluate with presence or absence of subscale in ＜ region within the μm of surface 10, away from crystal boundary ＞ is evaluated with presence or absence of Mn oxide in crystal grain within 1 μm
By SEM or tem observation, under conditions of multiplying power 20000 times, observe 5 randomly regard Open country, is carried out as desired by carrying out EDX analysis.
Operate the result obtained above by passing through and manufacturing condition is shown in table 2,3 in the lump.
[table 2-1]
Underscore is outside the scope of the invention
[table 2-2]
Underscore is outside the scope of the invention
[table 3-1]
Underscore is outside the scope of the invention
[table 3-2]
Underscore is outside the scope of the invention
From table 2,3, though utilize high-strength steel sheet that method of the present invention manufactures for a large amount of containing Si, The high-strength steel sheet of the easily oxidizable elements such as Mn, chemical convertibility, corrosion resistance, processability Also excellent.On the other hand, in a comparative example, in chemical convertibility, corrosion resistance, processability Any one is above the most poor.
Industrial applicability
The chemical convertibility of the high-strength steel sheet of the present invention, corrosion resistance, excellent in workability, can Utilize using the surface treated steel plate as the lightweight of vehicle body own and high intensity for making automobile.Separately Outward, beyond deaeration car, it is also possible to as the surface treated steel plate application that material plate is given rust-preventing characteristic In the field widely such as household electrical appliances, building material field.

Claims (4)

1. the manufacture method of a high-strength steel sheet, it is characterised in that containing in terms of quality % Have C:0.03～0.35%, Si:0.01～0.50%, Mn:3.6～8.0%, Al:0.01～ 1.0%, below P:0.10%, below S:0.010%, surplus is by Fe and inevitable impurity When the steel plate constituted carries out continuous annealing,
In the heating process of described continuous annealing, it it is 450 DEG C～A DEG C at annealing in-furnace temperature In temperature province, under conditions of programming rate is 7 DEG C/more than s, described steel plate is heated, Wherein, A:500≤A,
In described continuous annealing, steel plate maximum temperature reached is set to 600 DEG C～750 DEG C,
In described continuous annealing, at the steel plate of the temperature province that steel billet temperature is 600 DEG C～750 DEG C It is set to 30 seconds～10 minutes by the time, the dew point of atmosphere is set to more than-10 DEG C.
The manufacture method of high-strength steel sheet the most according to claim 1, it is characterised in that Described steel plate, contain further in terms of quality % selected from B:0.001～0.005%, Nb:0.005～ 0.05%, Ti:0.005～0.05%, Cr:0.001～1.0%, Mo:0.05～1.0%, Cu: 0.05～1.0%, Ni:0.05～1.0%, Sn:0.001～0.20%, Sb:0.001～0.20%, In Ta:0.001～0.10%, W:0.001～0.10% and V:0.001～0.10% a kind with On element be grouped into as one-tenth.
The manufacture method of high-strength steel sheet the most according to claim 1 and 2, its feature exists In, after carrying out described continuous annealing, in containing sulfur aqueous acid, carry out cathodic pickling.
4. a high-strength steel sheet, it is characterised in that there is the one-tenth described in claim 1 or 2 It is grouped into,
Have in the region within surface of steel plate 100 μm each one side add up to 0.010～ 0.050g/m2Selected from Fe, Si, Mn, Al, P, B, Nb, Ti, Cr, Mo, Cu, Oxide more than at least one in Ni, Sn, Sb, Ta, W and V,
Further in the region within surface of steel plate 10 μm within steel plate crystal boundary 1 μm There is in crystal grain the oxide containing Mn.
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